Building a Z-Wave Mesh Network

One of the biggest challenges in building out your Smart Home using a Home Automation Hub is the choice of devices. Not all devices work with each other; that’s where the Hub comes into play, connecting all different types of devices and bridging them together.

It can be a confusing soup of keywords out there with terms like WiFi, Bluetooth, ZigBee, Z-Wave, and many more. When planning or expanding your network, focusing on one type of network protocol can help with reliability and speed of your devices.

Z-Wave Networking Protocol

One of the more popular networking protocols for local devices is Z-Wave. You might have heard about the recent acquisition by Silicon Labs, which also makes ZigBee IoT sensors. Z-Wave is popular because it requires very little power, its command set is very public, and it is inexpensive to add to things like contact sensors, motion sensors, locks, and more.

Z-Wave works on the basic principle that there is a single controller that can ultimately talk to up to 232 “nodes”. Nodes can either be other controllers or end devices. Plugged-in nodes are also signal repeaters with the ability to repeat the signal to other nodes. These repeaters constitute the backbone of the mesh network. Battery powered nodes cannot repeat signals.

Below, we have two rooms. The hub is placed in the one room and we have a few Z-Wave devices in each room.

Z-Wave Mesh Network Example

The way the Z-Wave Mesh Network might represent this logically is like this:

Hub (ID 1)

|__ Motion Room 1 (ID 2)

|__ Outlet Room 1 (ID 3)

|__ Outlet Room 2 (ID 6)

|__ Motion Room 2 (ID 7)

|__ Dimmer Room 2 (ID 8)

|__ Lock Room 2 (ID 9)

|__ Dimmer Room 1 (ID 4)

|__ Contact Room 1 (ID 5)

Notice how the Outlet in Room 1 (ID3) is relaying the data for the other devices in Room 2. As a plugged-in device, it can act as a repeater. With signals able to repeat up to four times, this can provide strong coverage for a normal-sized home.

Z-Wave Can Extend Battery Life

Another significant benefit of Z-Wave is that battery-powered devices can essentially go to sleep and only wake up when needed; they don’t need to be constantly checking in if nothing has changed. This can extend battery life substantially. These end-point devices, like motion or contact sensors, or even button remotes, will reserve an ID on the pairing or joining process but will be offline until they need to wake up and send their information to the controller.

Including Devices in a Z-Wave Mesh Network

The Z-Wave process for including devices into a mesh network is called joining or inclusion. To build a strong mesh network, you need to include your repeater devices first. To start the process, put the device in join mode along with the controller. Once this process is complete, the security information is established and the device now belongs to that network. Moving a device from a previous Z-Wave mesh network typically requires either a factory reset or a process called exclusion. Any Z-Wave controller can be used to force a device to leave the mesh by placing itself in Exclusion mode. When in exclusion mode, a device can be allowed to forget its current mesh. This then allows it to be free to join a new mesh network.

Z-Wave Network Health via 'Repair'

The strength or health of a Z-Wave network is determined by a process called “Repair.” The main controller can start a “Repair” which optimizes the routes between nodes to ensure the fastest and cleanest connection. Every time you add a Z-Wave device, the mesh might branch off into a different direction. If you move devices around, running a repair will optimize your mesh network.

Given our previous mesh network above, after setting everything up and running a repair, the controller might optimize the mesh and it might end up looking like this:

Hub (ID 1)

|__ Motion Room 1 (ID 2)

|__ Outlet Room 1 (ID 3)

|__ Motion Room 2 (ID 7)

|__ Outlet Room 2 (ID 6)

|__ Dimmer Room 2 (ID 8)

|__ Lock Room 2 (ID 9)

|__ Dimmer Room 1 (ID 4)

|__ Contact Room 1 (ID 5)

How these routes are optimized is not important; just know that the logic is determined by each node and the controller to optimize the routing of information.

Z-Wave Mesh Networks Are Reliable

Z-Wave mesh networks are very reliable when set up properly and all devices are in range. The typical range for a Z-Wave device is up to 90 feet (30 meters) indoors, which can drop depending on how many walls or other obstructions that might be in the way. It is important to make sure you have enough powered nodes that can repeat the signal to the end of the network devices, such as locks. Setting up a solid mesh network is easy with the right number of devices, an understanding the limits and knowling how to use the tools (Join, Exclude and Repair). Once your mesh is set up, it will provide reliable and fast communication between your devices and your home automation controller.